Liquid crystal display and method for manufacturing same

Abstract

A liquid crystal display capable of reducing the occurrence of defective display due to variations in the initial alignment direction of a liquid crystal alignment control film in a liquid crystal display of an IPS scheme, realizing the stable liquid crystal alignment, providing excellent mass productivity, and having high image quality with a higher contrast ratio. The liquid crystal display has a liquid crystal layer disposed between a pair of substrates, at least one of the substrates being transparent, and an alignment control film formed between the liquid crystal layer and the substrate. At least one of the alignment control films 109 comprises photoreactive polyimide and/or polyamic acid provided with an alignment control ability by irradiation of substantially linearly polarized light.

What is claimed is: 
     
       1. A method of manufacturing a liquid crystal display device, the liquid crystal display device having:
 a first substrate having a thin film transistor, a transparent pixel electrode connected with the thin film transistor, and a transparent common electrode; 
 a second substrate opposed to the first substrate; 
 a liquid crystal layer between the first substrate and the second substrate; 
 a photo alignment control film between the first substrate and the liquid crystal layer; 
 a common electrode wire supplying a voltage to the transparent common electrode; 
 a protective layer between the transparent common electrode and the common electrode wire and having a through hole; and 
 a pair of scanning signal wires and a video signal wire supplying a video signal to the transparent pixel electrode, 
 the method comprising forming the photo alignment control film by a heating step performed to overlap in time with an irradiation of polarized light toward a film including polyamic acid or polyimide comprising cyclobutanetetracarboxylic acid dianhydride and aromatic diamine after imidization, 
 wherein the transparent pixel electrode has a linear portion, 
 wherein the linear portion and the video signal wire have a bended portion between the pair of plurality of scanning signal wires, 
 wherein a contrast ratio is equal to or higher than 500:1, 
 wherein a time for eliminating after-image is 5 minutes or shorter, 
 wherein an anchoring energy in the azimuth direction at an interface of the photo alignment control film and the liquid crystal layer is 2.3×10 −4  N/m or more, 
 wherein the transparent common electrode is electrically connected with the common electrode wire via the through hole, 
 wherein the photo alignment control film is formed in the through hole, 
 wherein the cyclobutanetetracarboxylic acid dianhydride is represented by a formula [18] 
 
       
         
           
           
               
               
           
         
         wherein the aromatic diamine compound is represented by a formula [19], [20], or combination thereof 
       
       
         
           
           
               
               
           
         
       
     
     
       2. The method of manufacturing a liquid crystal display device according to  claim 1 , wherein the transparent common electrode is between the transparent pixel electrode and the photo alignment control film. 
     
     
       3. The method of manufacturing a liquid crystal display device according to  claim 1 , wherein the photo alignment film has a glass transition temperature equal to or higher than 250° C. 
     
     
       4. The method of manufacturing a liquid crystal display device according to  claim 1 , wherein the photo alignment control film has a thickness from 1 nm to 100 nm. 
     
     
       5. The method of manufacturing a liquid crystal display device according to  claim 1 , wherein the polyimide comprises a plurality of aromatic diamines. 
     
     
       6. The method of manufacturing a liquid crystal display device according to  claim 1 , wherein the photo alignment control film is formed on a surface including a step having a height of 0.1 μm or larger. 
     
     
       7. A method of manufacturing a liquid crystal display device, the liquid crystal display device having:
 a first substrate having a thin film transistor, a transparent pixel electrode connected with the thin film transistor, and a transparent common electrode; 
 a second substrate opposed to the first substrate; 
 a liquid crystal layer between the first substrate and the second substrate; 
 a photo alignment control film between the first substrate and the liquid crystal layer; and 
 a pair of scanning signal wires and a video signal wire supplying a video signal to the transparent pixel electrode, 
 the method comprising forming the photo alignment control film by a heating step performed to overlap in time with an irradiation of polarized light toward a film including polyimide comprising cyclobutanetetracarboxylic acid dianhydride and aromatic diamine after imidization, 
 wherein the transparent pixel electrode has a linear portion, 
 wherein the linear portion and the video signal wire have a bended portion between the pair of plurality of scanning signal wires, 
 wherein a contrast ratio is equal to or higher than 500:1, 
 wherein a time for eliminating after-image is 5 minutes or shorter, 
 wherein an anchoring energy in the azimuth direction at an interface of the photo alignment control film and the liquid crystal layer is 2.3×10 −4  N/m or more, 
 wherein the transparent pixel electrode directly contacts the photo alignment control film, 
 wherein the cyclobutanetetracarboxylic acid dianhydride is represented by a formula [18] 
 
       
         
           
           
               
               
           
         
         wherein the aromatic diamine compound is represented by a formula [19], [20], or combination thereof 
       
       
         
           
           
               
               
           
         
       
     
     
       8. The method of manufacturing a liquid crystal display device according to  claim 7 , wherein the transparent common electrode is between the transparent pixel electrode and the first substrate. 
     
     
       9. The method of manufacturing a liquid crystal display device according to  claim 7 , wherein the photo alignment film has a glass transition temperature equal to or higher than 250° C. 
     
     
       10. The method of manufacturing a liquid crystal display device according to  claim 7 , wherein the photo alignment control film has a thickness from 1 nm to 100 nm. 
     
     
       11. The method of manufacturing a liquid crystal display device according to  claim 7 , wherein the polyimide comprises a plurality of aromatic diamines. 
     
     
       12. The method of manufacturing a liquid crystal display device according to  claim 7 , wherein the photo alignment control film is formed on a surface including a step having a height of 0.1 μm or larger. 
     
     
       13. The method of manufacturing a liquid crystal display device according to  claim 1 , wherein the aromatic diamine compound is represented by a formula [20] or combination of formula [19] and [20].